I. Field of the Invention
The invention relates to hydraulic pumps in general and to positive displacement, air-hydraulic, reciprocating piston pumps with pressure controls in particular.
II. Description of the Prior Art
My aforementioned patent describes a new and improved double acting, air operated pump automatically operable to switch over from high volume-low pressure operation to low volume-high pressure operation upon a predetermined back pressure being produced.
The present invention provides an improvement over the construction disclosed in my aforementioned patent in that it describes a substantially simpler construction for such pumps. In my prior device, the hydraulic piston and the air piston were fashioned from a single piece of material. The concentricity requirements of such a construction make it expensive to produce. The present invention provides a construction in which it is easier and thus more economical to maintain the required relationship between the piston and their chambers.